Most headphones are passive, therefore the performance depends on the external amplifier that is used. Therefore, the performance varies a lot from unit to unit and from design to design. There are some active headphones with electronics built into the earphone cups. Electronics is taking space and reducing acoustic performance (often). Electronic functions are just amplifier, or amplifier and ANC (Active Noise Cancellation). Getting the necessary interfaces for computer/digital audio/analog audio is expensive. There are two types of headphones: open and closed headphones. While the open headphones have their own advantages they have poor attenuation for the environmental noise and this can prevent hearing of details in the audio material (and the environment acoustics may even affect the audio of the headphones), but the open headphone design is said to avoid the “box” sound (audio colorations) and limited low frequency extension sometimes associated with the closed headphones design. Also in the closed headphone the user hearing is limited to the ear cup area and therefore communicating between users might be a challenging.
When the headphones are used to complement and continue the work also done using loudspeakers there is a need to design headphone and the associated signal processing such that the calibration of the headphone has the same sound character as a the sound of the loudspeaker based monitor system in a room so that the sound quality could stay consistent when switching from one system to another.